The present invention relates generally to an electrical connector and, more particularly, to a grounding ring for an electrical connector which provides protection against RFI/EMI signals.
The use of shielding in electrical connectors to prevent unwanted radio frequency and electro-magnetic signals (RFI/EMI) from interfering with signals being carried by the contacts in connectors is well known. U.S. Pat. Nos. 3,521,222; 3,678,445; 3,897,125; 4,106,839 and 4,239,318 disclose annular shields formed of sheet metal with resilient fingers which electrically engage the outer surface of the plug barrel and the inner surface of the receptacle shell of the electrical connector.
U.S. Pat. No. 3,835,443 discloses an electrical connector shield comprising a helically coiled conductive spring which is interposed between facing annular surfaces on the mating halves of an electrical connector. The spring is coiled in such a manner that the convolutions thereof are slanted at an oblique angle to the center axis of the connector members. When the connector members are mated, the spring is axially flattened to minimize the gap between the convolutions thereof and to provide a wiping electrical engagement with the annular surfaces on the mating halves of the connector.
U.S. Pat. No. 4,033,654 discloses another form of slant coil spring shield for an electrical connector in which the spring is mounted in an internal groove formed in the receptacle shell. The convolutions of the spring are arranged in such a fashion that they will collapse radially when the plug barrel is inserted into the receptacle shell.
Each of the foregoing shielding devices has the disadvantage that slots or gaps exist in the device which allow some EMI/RFI leakage into the connector. Also, the devices are costly and damage sensitive.
U.S. Pat. No. 3,336,566 discloses a coaxial connector embodying a two layer contact member for preventing signal leakage from the interior of the connector. The two layers embody reversely bent, overlapping spring fingers. The fingers of one layer are offset from the fingers of the other layer so that the fingers of each layer overly the boundaries formed between the fingers of the other layer to provide a generally continous contact member. The resilient fingers expand radially outwardly when a tubular conductive member on a coaxial cable is pushed into the interior of the contact member. While this double layer arrangement provides a peripherally continuous shield, it is expensive to manufacture and the slits in the two layers of the contact member which form the resilient fingers provide sharp edges which is undesirable.
It is the object of the present invention to provide a simple, inexpensive and effective grounding ring for an electrical connector which provides a windowless EMI/RFI shield between the mating halves of the electrical connector at their interface.